Ionic Requirements of Treponema Pallidum

DOAK, G. 0. (University of North Carolina, Chapel Hill), LEON D. FREEDMAN, AND JOHN W. CLARK, JR. Ionic requirements of Treponema pallidum. III. Divalent ions. J. Bacteriol. 82:909912. 1961.-Suspensions of Treponema pallidum, prepared by extracting the testes of syphilitic rabbits with normal rabbit serum or with a culture medium, were shaken with Amberlite IRC-50 resin in the sodium ion form. This procedure did not noticeably reduce the number of motile organisms, but markedly decreased their ability to survive in vitro. The addition of calcium, strontium, or barium ions to the treated suspensions largely restored this loss of motility. These same ions, when added to suspensions of T. pallidum not treated with the ion exchange resin, were without effect. Magnesium ion also had a beneficial effect, but considerably less than that produced by calcium ion. Cobaltous, manganous, ferrous, and zinc ions gave no beneficial effect, and, except for manganous ion, were toxic to the organisms at 5 X 10-3 M. In two previous papers from this laboratory (Doak, Freedman, and Clark, 1959a,b), the effect of monovalent positive ions in prolonging the motility of Treponema pallidum in vitro has been elucidated. Weber (1960) has confirmed our observation that sodium ion is of value in prolonging the in vitro survival time of T. pallidum; but, at least under conditions of his experiments, he could not confirm our results on the toxic effect of sodium ion in concentrations above 0.029 M. The reason for this discrepancy is at present under investigation in this labora-